CCNA Practice Test 20 — 15 Questions

Question 1

Exhibit: After a new switch was connected, the access-layer port went into err-disabled state immediately. Which feature most likely caused this?

Accepted Answer

BPDU Guard. BPDU Guard is the most likely cause because it immediately places a PortFast-enabled port into the err-disabled state upon receiving any BPDU, which is exactly what happens when a new switch is connected to an access port meant for end devices. Root Guard does not err-disable a port; instead, it puts the port into a root-inconsistent state when a superior BPDU is received, preventing the port from becoming a root port but still allowing traffic. UDLD aggressive can cause err-disabled states, but it is specifically designed to detect unidirectional links on fiber connections and requires a delay or misconfiguration, making it less immediate than BPDU Guard in this scenario. Storm control can err-disable a port if traffic exceeds thresholds, but this is not immediate upon connection unless a broadcast storm is already occurring, which is not indicated in the scenario.

Answer

Root Guard

Answer

UDLD aggressive

Answer

Storm control

Question 2

A switch should learn one MAC address on an access port and shut the port down if a second unauthorized device appears. Which two port-security settings support that requirement?

Accepted Answer

switchport port-security maximum 1. Port security enforces how many MAC addresses may be learned on a port and what happens when a violation occurs. 'switchport port-security maximum 1' limits the port to one MAC address, and 'switchport port-security violation shutdown' disables the port if a violation occurs, matching the requirement. 'switchport protected' isolates ports within a switch but does not limit MAC addresses or cause a shutdown. 'switchport nonegotiate' disables DTP negotiation, which is unrelated to port security.

Answer

switchport protected

Answer

switchport nonegotiate

Question 3

Match each IPv4-related concept to its most accurate role.

Accepted Answer

IPv4 address. The subnet mask defines the network and host portions of an IP address, allowing a host to determine which destinations are on the local subnet versus remote. The default gateway is the local router that forwards traffic destined for other subnets. The broadcast address is used to send a packet to all hosts within the local subnet simultaneously. The host address uniquely identifies one specific device on that subnet.

Answer

Subnet mask

Answer

Default gateway

Answer

DNS server

Question 4

Which STP port state on a classic 802.1D switch listens for BPDUs and prepares to participate in the topology, but does not yet learn MAC addresses?

Accepted Answer

Listening. In classic STP, the listening state processes BPDUs and waits before learning begins. The learning state is when the switch starts populating the MAC table.

Answer

Learning

Answer

Forwarding

Answer

Disabled

Question 5

Drag and drop the following steps into the correct order to describe the data encapsulation process as it flows down the OSI model from the source host.

Accepted Answer

Application data is generated and passed to the Transport layer.. Encapsulation proceeds from the top OSI layers to the bottom. First, the application generates data (Step 1). The Transport layer then adds a header (TCP or UDP) to create a segment (Step 2) because this is the first step in preparing data for reliable delivery. The Network layer adds an IP header to form a packet (Step 3), which provides logical addressing and routing information. The Data Link layer adds a frame header and trailer to create a frame (Step 4), enabling physical addressing (MAC) and error detection. Finally, the Physical layer converts the frame to bits for transmission (Step 5), as it is the layer that ultimately puts signals on the wire.

Question 6

A user reports that the corporate SSID is visible and accepts the correct password, but the client always lands in a quarantined remediation network. Which troubleshooting area is strongest?

Accepted Answer

Post-authentication policy, role, or VLAN assignment logic. The strongest troubleshooting area is post-authentication policy or role assignment. The client already sees the SSID and successfully authenticates, so the problem is not RF visibility or password failure. Landing in a remediation network indicates a policy decision after authentication, such as a mismatched VLAN assignment or client role. Option B (hidden SSID) is irrelevant because the SSID is visible. Option C (PPP encapsulation) does not affect post-authentication network placement. Option D (OSPF DR election) is unrelated to client VLAN assignment.

Answer

Whether the SSID is hidden instead of broadcast

Answer

Whether the AP uplink uses PPP encapsulation

Answer

Whether OSPF designated routers are elected correctly

Question 7

Drag and drop the following steps into the correct order to troubleshoot a client PC that cannot connect to a remote web server.

Accepted Answer

Run ipconfig /all to verify the PC's IP address, subnet mask, and default gateway.. The correct order follows Cisco's bottom-up troubleshooting methodology: first verify local IP configuration with ipconfig, then confirm the local TCP/IP stack with a loopback ping, then verify the NIC and IP binding by pinging the assigned address. Next, test connectivity to the default gateway to ensure the local subnet and router are reachable. After that, attempt to reach the remote server's IP address with ping. If that fails, use traceroute to identify where along the path the packets are lost. This sequence efficiently isolates the fault domain from the local device to the internetwork.

Question 8

Drag and drop the following steps into the correct order to configure Rapid PVST+ with a designated root bridge, PortFast, and BPDU Guard on access ports.

Accepted Answer

Set the spanning-tree mode to Rapid PVST+. 1. Set the spanning-tree mode to Rapid PVST+: This enables Rapid PVST+ globally, a prerequisite for the root primary command to function correctly. 2. Configure the switch as the root bridge for VLAN 1: Lowers the bridge priority to guarantee this switch becomes the root, defining the STP topology. 3. Enter interface configuration mode for the access ports: Prepares the specific ports where PortFast and BPDU Guard are applied. 4. Enable PortFast on the interfaces: Allows immediate transition to forwarding state, bypassing listening/learning phases. 5. Enable BPDU Guard on the interfaces: Protects the network by err-disabling the port if a BPDU is received, which should occur only after PortFast is enabled on access ports.

Question 9

Drag and drop the following steps into the correct order to configure a Windows 10 host with a static IPv4 address, subnet mask, and default gateway.

Accepted Answer

Open Control Panel and navigate to Network and Sharing Center.. The correct order begins with opening Network and Sharing Center to access network settings. Then, you must click 'Change adapter settings' to see the list of network connections. Right-clicking the appropriate adapter and selecting Properties opens its configuration. Selecting IPv4 and clicking Properties allows you to set the IP parameters. Choosing 'Use the following IP address' enables the fields for static input. Finally, entering the IP address, subnet mask, and default gateway followed by OK/Close applies the configuration. This sequence follows the logical navigation of the Windows GUI to reach the static IP assignment interface.

Question 10

Drag and drop the following steps into the correct order to troubleshoot a fiber optic link that is down on a Cisco switch using SFP transceiver diagnostics and interface commands.

Accepted Answer

Physically verify the fiber cable connectors are clean, undamaged, and correctly mated with the SFP transceiver.. The logical troubleshooting sequence moves from simple physical checks to detailed diagnostics. Step 1 verifies the most basic physical layer (cable and connectors). Step 2 confirms the SFP compatibility and seating. Step 3 checks the interface administrative and protocol status. Step 4 inspects optical levels, which can only be meaningful if the interface is up and the SFP is recognized. Step 5 examines error counters for deeper layer‑1 issues. This order follows Cisco’s recommended troubleshooting methodology: physical → transceiver → interface status → optical diagnostics → error counters.

Question 11

Drag and drop the following steps into the correct order to configure a router-on-a-stick topology for inter-VLAN routing between VLANs 10 and 20, using 802.1Q trunking with native VLAN 99 for management traffic.

Accepted Answer

Create VLANs 10, 20, and 99 on the switch.. The sequence follows Cisco's best practices: VLANs are created first, then access ports are assigned to them. The switch trunk is configured with 802.1Q encapsulation and the native VLAN set to 99 before the router end. On the router, the physical interface must be enabled before subinterfaces can operate. The native VLAN subinterface is created first to handle untagged frames, then the data VLAN subinterfaces are configured. This order avoids errors such as missing VLANs, incorrect encapsulation, and physical link down state.

Question 12

Drag and drop the following steps into the correct order to troubleshoot a suspected duplex mismatch and CRC errors on a Cisco switch interface.

Accepted Answer

Enter privileged EXEC mode using the 'enable' command.. Troubleshooting starts from privileged EXEC, checking errors, identifying the problematic interface, then configuring the correct duplex setting.

Question 13

A phone and a PC are attached to the same switchport. The intended data VLAN is VLAN 10, and the phone uses voice VLAN 20. The switchport currently has `switchport voice vlan 20` configured. The phone works, but the PC cannot reach the data network. Which command is most likely missing?

Accepted Answer

switchport access vlan 10. When a Cisco IP phone and a PC share one port, the switchport often needs both a data VLAN and a voice VLAN. If the voice VLAN exists but the data access VLAN is wrong or missing, the phone can work while the PC fails.

Answer

switchport mode dynamic auto

Answer

switchport voice vlan 20

Answer

spanning-tree guard root

Question 14

Drag and drop the following steps into the correct order to diagnose and resolve a duplex/speed mismatch causing interface errors on a Cisco switch.

Accepted Answer

Enter the 'show interfaces' command to examine interface status and error counters.. The correct diagnostic process begins by collecting interface statistics with 'show interfaces' to detect anomalies (step 1). If CRC errors, runts, and late collisions are present, these indicate a duplex mismatch (step 2). Next, check the current duplex and speed configuration for that interface using 'show interfaces <int>' (step 3). Compare this setting with the expected configuration or with the remote device's interface (step 4) to confirm the mismatch. Based on the findings, apply the correct duplex and speed commands to align both ends (step 5). Finally, verify that the error counters stop incrementing after the fix (step 6).

Question 15

Drag and drop the following steps into the correct order to troubleshoot a Windows client that is unable to reach a remote server.

Accepted Answer

Run ipconfig /all to check IP configuration, subnet mask, default gateway, and DNS servers.. The correct order begins with ipconfig /all to verify the client's IP settings, then tests the local TCP/IP stack with ping 127.0.0.1. Next, pinging the client's own IP confirms the NIC and configuration. Pinging the default gateway checks local network connectivity, and pinging the remote server tests end-to-end. Finally, tracert isolates the failure point if the remote ping fails. This layered approach narrows the problem scope from the host itself outward.